The present disclosure relates generally to an arrangement for, and a method of, reading radio frequency (RF) identification (RFID) product tags associated with products in a venue in real time with an enhanced performance, especially for rapidly and accurately locating and tracking such RFID product tags associated with products located in zones of interest in the venue.
It is known to deploy a radio frequency (RF) identification (RFID) system in a retail, factory, or warehouse environment, or a like controlled area or venue, for product locationing, product tracking, product identification, and inventory control. For example, in order to take an inventory of products associated with RFID product tags in a warehouse environment or venue, it is known to position a plurality of RFID tag readers or sensing network units at overhead, fixed locations, on the ceiling, or at doorways, loading docks, and assembly lines, in the venue, and then, to operate each such reader, under the control of a network host computer or server, to form and steer an interrogation beam, both in azimuth, e.g., over an angle of 360 degrees around a vertical axis, and in elevation, e.g., over an angle of about 90 degrees away from the vertical axis, over a coverage range across any such product tags to read their payloads. Each RFID product tag is usually attached to, or associated with, an individual product, or to a package for the product, or to a pallet or container for multiple products, or to a freight mover, such as a forklift or truck, for moving such products, packages, or pallets in the venue. Each RFID product tag typically includes a tag antenna, a power management section, a radio section, and frequently a logic section, a memory, or both. A multitude of such product tags may be in the coverage range of each RFID reader.
In brief, each RFID reader transmits an RF interrogating signal, and each RFID product tag, which senses the interrogating RF signal, responds by transmitting a return RF signal. Each RFID product tag either generates the return RF signal originally, or reflects back a portion of the interrogating RF signal in a process known as backscatter. The return RF signal may further encode data stored internally in the product tag. The return signal is demodulated and decoded into identification data (also known as the payload) by each reader, which thereby identifies, counts, or otherwise interacts with the associated product. The decoded data can denote a serial number, a price, a date, a destination, a location, other attribute(s), or any combination of attributes, and so on. A specific location of any particular RFID-tagged product in the venue is typically determined by having the server process the payloads and capture data from a plurality of such RFID readers by using triangulation/trilateration techniques known in the art.
As advantageous as such known RFID systems have been in identifying, locating and tracking products with RFID product tags, especially low-cost passive tags, it has proven difficult in practice to accurately and rapidly locate each product tag, especially when one or more of the product tags have moved, as well as when there is a multitude, e.g., a product tag population of many thousands, of such product tags in the venue. In addition, the venue itself has structures, such as shelving and like fixtures, as well as walls, the floor and the ceiling, and even people and moving equipment, all of which and more can reflect and/or scatter and/or absorb the RF signals, thereby causing the RF signals to travel along multiple, disrupted, folded paths and negatively impacting the travel of the RF signals between the RFID product tags and each RFID reader. Each RFID reader reads at a certain read rate, for example, about 100-200 product tags per second, and it takes a certain, non-negligible amount of time to read an entire product tag population. Sometimes, each RFID reader has to read an individual product tag more than once to accurately determine its location. When an RFID-tagged product has moved, i.e., when its location has changed to a new location, the time that it takes to provide an update of its new location is negatively affected by the presence of a large number of other product tags. It is not always possible to know, at least not immediately, when a particular product tag has moved, because the system must typically identify and locate all the product tags before it can determine whether any particular product tag has moved. The amount of time it takes to determine the new location of a product tag that has moved is a linear function of the number of the product tags within the coverage range of the reader(s). Real time reading performance, on the order of one second or less, for rapidly determining the new location of a product tag that has moved, or for accurately locating any particular product tag, is a challenge that known RFID systems have not always adequately met.
In addition, there are crucial times during RFID system operation when, and/or crucial sites in the venue where, it is essential to accurately and rapidly locate and track the product tags. For example, during merchandise stock movement of products being unloaded at unloading bays in the venue, or being replenished on shelves in the venue, or being moved from a backroom onto a sales floor, or being unpacked to a storage area, and so forth, missed and/or misdirected product tag reads at such crucial sites and at such crucial times can result in inaccurate inventory estimates, which is an important concern for all businesses, especially retailers. Overstating inventory hurts sales and adversely affects shopper satisfaction. Understating inventory triggers orders for more merchandise, thereby resulting in overstocked storerooms. Countless person-hours are spent in accounting for missing or misplaced products due to unreliable, inaccurate, and untimely inventory counts.
Accordingly, there is a need to more accurately and rapidly locate such product tags, especially at crucial times during RFID system operation and/or at crucial sites in the venue, and to enhance the reading performance of such RFID systems.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and locations of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The arrangement and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.